The oxidative coupling of methane (OCM) is among the most studied reaction for methane upgrading in the past four decades. Although the OCM reaction is exergonic, the maximum C₂ product yield has been limited to <30% yield largely due to combustions issue. Among the hundreds of reported catalysts, Li/MgO, La-based, and Mn/Na₂WO₄/SiO₂ catalysts exhibit the highest OCM performance. High C₂ yield and excellent long-term stability have been reported on the Mn/Na₂WO₄/SiO₂ catalyst. However, because of the structural complexity, the roles of each component in the catalyst have been controversial, which hinders the rational design of OCM catalyst with improved performance.

In this work, WO_x and MnO_x sites were grafted on well-defined Na₂Ti₅O₁₁ nanowires and employed in OCM studies. Compared to the commonly used silica support, Na₂Ti₅O₁₁ exhibit superior intrinsic thermal stability and facilitates straightforward structural characterizations such as advanced electron microscopy. MnW/ Na₂Ti₅O₁₁ inherits high activity from Mn/ Na₂Ti₅O₁₁ and high C₂ selectivity from W/ Na₂Ti₅O₁₁, clearly demonstrating the synergistic effect between WO_x and MnO_x sites. The catalytic performance of the MnW/ Na₂Ti₅O₁₁ is similar to that of a standard reference catalyst, Na₂WO₄-MnO_x/SiO₂, suggesting that these nanowire-based catalysts can be employed as model catalysts for studying the synergistic effect between MnO_x and WO_x sites.

Divakar Reddy Aireddy

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